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Why the Earth's Core Is Hotter Than the Sun

[Music]

you know we've managed to go hundreds of

thousands of miles into space but when

it comes to the earth we've barely

scratched the surface our planet's core

is a magnificent mystery filled with

secrets well it's time to figure them

out the Earth's inner core is an

extra-hot solid ball with an approximate

radius of 760 miles to put that into

perspective

it's just 30% smaller than the moon but

if we've never been there how did we

find this out well we've learned about

the core by observing the effects of

gravity on objects on the surface of our

planet from there it's estimated that

the Earth's mass is 5.6 sextillion tons

get at your bathroom scale

now don't the density of everything that

lies on the surface is much lower than

the cores average density scientists

figured out that most of the Earth's

mass is located towards the center of

our planet it's estimated that more than

80% of the core consists of one of the

ten most common elements in our galaxy

fire but the iron on the Earth's surface

is kind of limited I know what you're

wondering how did the iron make it all

the way down to the core well there is a

simple explanation the heavy elements

somehow pushed itself literally towards

the center of the earth and at I'm

pardon the pun of research was done to

figure out how most of the earth's

surface is made of rocks called

silicates and the molten iron had some

difficulty passing through them to help

you understand think of how water

struggles to get through a greasy

surface but in 2013

Wendy Mao and her team from Stanford

discovered a possible solution for how

this happened they began an experiment

to see how iron and silicate react when

they're exposed to extreme pressure like

that in the core they used a diamond

anvil cell to pinch the two substances

under those conditions and they achieved

it the pressure was 330 Giga Pascal's

which is around 3.3 million times the

atmospheric pressure

our planet the molten iron slowly

squeeze through the silicate rocks and

they had their answer it took millions

of years for the iron to reach the

center so it happened at a snail's pace

since snails weren't around back then

the iron had to guess how fast to go

well now that we have that figured out

how do we know what size the core is

that's when seismology comes into play

during an earthquake

shockwaves are spread through the planet

seismologists studied these vibrations

and tried to read the reflections on the

other side

it's like Thor is hitting one side of

the planet with his hammer and the

seismologists are listening from the

opposite end but these vibrations also

take different routes they go through

various parts of the planet and that

affects the sound they make at the end

let's take a small detour for a minute

seismology is quite an old scientific

field in the old days when vibrations

occurred scientists noticed that

something was wrong with them these

vibrations were s waves and when they

were supposed to show up on the other

side they just vanished at first they

thought that something was wrong with

her equipment and it just wasn't picking

up the vibrations but as science

progressed it turned out that these

picky s waves could only go through

solid material and not liquid so

something molten was present in the

center of the earth

that was preventing the vibrations from

going through so they started digging

into their data they mapped out the

paths of the seismic waves and found

that around 1800 60 miles from the

Earth's surface the rocks transformed

into a liquid but there's also an

interesting fact in the game angle Amon

was a Danish seismologist and in the

1930s she discovered a new wave pattern

first we had the S waves that didn't

pass through a liquid but then there

were also P waves that could travel

through the core and appear on the

opposite side of the planet

that was when Inga came up with a theory

that the core has two layers the solid

inner core which is around 3,700 miles

below the surface and the molten outer

core

which is around 1860 miles below our

feet when advanced seismographs were

invented her theory was confirmed but

that took 40 years so now that we have

the structure figured out let's talk

about how hot the core is and why we've

already established that we can't put a

thermometer down there to study the

temperatures so scientists tried to

figure that out by creating the same

crushing pressures in their labs again

in 2013 a team of French researchers

came up with the most accurate number

that we've had in years

they put pure iron through high pressure

almost higher than that of the core to

come up with their findings the

temperature of the inner core is about

nine thousand eight hundred degrees

while the melting point of pure iron is

about twenty-eight hundred degrees at

the core its melting point is around

eleven thousand degrees the fluctuation

in those temperatures comes from

factoring in the extreme pressure the

iron is exposed to at the core also

other elements inside the core could be

bringing the temperature down by

approximately 400 degrees but the reason

it remains solid is because of the slow

cooling of the outer core and it's

compression the inner core spins faster

than the earth that's caused by the

thermal activity inside our planet which

creates the magnetosphere oddly it takes

a ton of time pardon the pun for heat to

leave the earth but I'll get to that in

a bit

there are three main reasons why the

earth is still boiling the first one is

that the core has remained hot from the

time our planet was formed roughly

four-and-a-half billion years ago

remember that number because towards the

end I'll explain how that happened

that heat hasn't been lost yet in fact

the earth is only cooling down around

200 degrees every billion years secondly

it generates heat from the friction of

the dense materials as they move and the

last reason it's so high is from the

decay of radioactive elements so why is

this important it makes it easy for

scientists to understand how it affects

the speed of vibrations that go through

the core

remember the p-waves I told you about

earlier well these guys travel slower

than they should while passing through

the core this shows that there must be

some other element in there that we

haven't figured out yet nickel is one of

them but when scientists ran some tests

with nickel the p-waves didn't slow down

enough so they started digging

metaphorically in 2015 a new study from

Durham University came out it claimed

that 90% of the Earth's sulfur is in the

core so maybe that could be the missing

element around four-and-a-half billion

years ago the earth collided with a

large planetary body that eventually

tore apart our planet and formed the

moon that incident left traces behind

that led the studies in a new direction

when the impact happened the Earth's

mantle melted and some sulfur rich

liquids squeezed through the ruins and

reformed it some of it was probably lost

in space but the rest sunk to the core

scientists from Durham University

confirmed that theory by measuring the

isotope ratios of elements in the mantle

they compared them to meteorites which

were possibly part of the Earth's

original form the problem was that there

were so many different elements in the

mantle it's quite difficult to draw firm

conclusions so they came up with another

idea

copper is usually bound to sulfur so

they analyzed the copper from the

Earth's mantle and crust now this was a

three-stage study done in different labs

using state-of-the-art mass

spectroscopes

yes still with me here good for you they

found that there was a teeny tiny

difference in the copper ratios between

the Earth's mantle samples and the

meteorite samples that confirmed the

theory that the earth originally

collided with another body

and most of its mantle just splattered

around space we also know that the core

consists of some sulfur hopefully soon

we'll be able to find out what the other

trace elements are so to answer your

final question yes the center of the

earth is hard core yes you were waiting

for that one weren't you hey if you

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